Phosphate product and method of making same



1951 R. w. LIDDELL 2,569,936

PHOSPHATE PRODUCT AND METHOD OF MAKING SAME Filed Nov. 8, 1947 2Sheets-Sheet 1 u II WITNESSES: INVENTOR KM. I

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4&4, ATTORN EY o 9 R. w. LIDDELL 2,569,936

PHOSPHATE PRODUCT AND METHOD OF MAKING SAME 2 Sheets-Sheet 2 Filed Nov.8, 1947 U 44 45 Lmm1 2 WITNESSES: INVE TOR WQW ATTORNEY Patented Oct. 2,1951 UNITED STATES PATENT OFFICE PHOSPHATE PRODUCT AND METHOD OF "MAKINGSAME .Itobert W. Liddell, .Bethel Township, Allegheny County,Pa.,assignor to Hall Laboratories, Inc.,

Claims. 1 This invention relates to a new form of water soluble hardnesssequestering phosphate as an article otmanuiacture andto aprocess ofmanufacturing such article.

=More specifically, my product, as a new .article (of manufacture, is analkali-metal phosphate Ihaving among other properties, .the hardnesssequestering propertiesof the alkali-metal phos- ,phate glasses and.crystalline tripolyphosphate,

5 fromsuitable starting materials such as hereinafter described.

The starting materials may be charged into the furnace at anyappropriate point such as through an opening 2 inthe back of thefurnace. These abut whose physical structure or form is cellularmaterials aremelted in a chamber 3 which is :orfoam-like, and extremelyrapidly-soluble when added-directly towa-ter. The method of thisinwention is directed to the 'manner in which the sstarting materialsare treated and used in order tto-produce-an alkali-metalphosphatehaving a cellular or :foam-like physical structure or .form.

:An object of this invention is to provide a ;phosphate product that israpidly soluble in water. A

Another :ebaectof theinvention is to provide a phosphate product whichwill dissolve substantiallycompletely inarelatively short period of timemeasured in terms of seconds forexample, in-the length of time requiredfor the material to :sink to a depth of four-to-eight inches onbeingdropped into a body-of water.

A s'till'further objectof theinvention is to-provide a glassyalkali-metal phosphate which is light and has 'a sponge-like or cellularstructure .heated to the desired or necessary temperature obtained byproper control of burners '4, prefer- .ably gas burners. .The moltenphosphate flows from chamber 3 under abridge wall 5 into a 15 chamber 6in which the melt is thoroughly heated through and brought to thedesired temperature for further processing. The .matter of temperatureof the melt is'hereinafter more particularly described.

Chamber Bis likewise heated by gas burners I, the fuel input to which isadjusted to obtain the :desired heatingcr cooking .of the melt before'itis discharged fromtheiurnace. The length of chamber 6 may also bedesigned to insure .a

thorough cooking and mixing of the melt as the melt fiows towards theoutlet of the furnace to properly condition the .melt .before it isfurther .processed with gas-liberating materials. .The molten-phosphateflows from chamber 6 down a sand is extremely rapidly soluble whenmerely trough B from which the melt is discharged into addedto water.

:A still furtherobiect of'the invention is to pro- :vide a method ofmaking a. phosphate product .having theproperties above set forth.

-receptaclescarried by a rotary table 9. If necessary to preventprechilling or excessive loss of heat from .the melt=as it flows downtrough 8, (heat may be applied .to the trough by means of i0ther objectsof the invention will, in part, be '35 a'gas burner iii. .A gate .II .isprovided at the apparent and will, in part, be obvious-from "thefollowing description taken in conjunction with theaccompanying-drawings inwhich:

Figure 'l iswmore or less schematic view in iongitudinal section-of a:furnace in which the-.40 wphosphate -melt is produced and a fragmentary-view'partia11y .in section of apparatus for pro -ducing the product of=the invention from the melt, which apparatus .is employedas well in.dischargeendoftrough B to permit shutting off :the Ilow of phosphatemelt to accommodate charging of the reaction vessels on table '9.

In Fig.2, table! is shown as having aplurality of reaction vessels l2 to45, inclusive, uniformly -spaced .on -.the table along its periphery.

.Ihegas-liberating materials .may Joe placed in the reaction vessels l2to l5, inclusive, either before the phosphate melt is poured into themcarrying out the method oriprooess of theainvenor at the same time, orsubsequent to the pouring :tion; and

2 is a-top-view of arevolving table (shown partially ill-Fig.1):provided with reactionvessels into which molten phosphate andgas-liberating materials are charged;.-and

Fig. 3 is a view :in'longitudinal section taken [on line III-III of lotthe :revolving table -as shown in connection with a .rolling andquenching table onto'whichthe :materiahin the I warious reaction-vesselsle -ejected.

of the .melt. However, as shown in Fig. 2, the arrangement such that thegas-liberating ma- .terialsare charged into the reaction vessels aheadof the charging .of the phosphate melt. One or .150 more feeders I 6,see Figs. 2 and 3, may be employedior depositingmeasured quantitiesofgasliberating material into the reaction vessels'before or as theyreach station l'l. As the table advancesclockwise, a..reaetion vesselcontaining gas-liberating .material comes .to position under thedischarge end of trough 8, in which position a measured amount of meltis poured into the reaction vessel. The table is then advanced to bringthe next reaction vessel to the place where the phosphate melt will flowinto it. Meanwhile, a stirring mechanism I8 is placed over the vesselcontaining phosphate melt and gas-liberating material with a stirrer l8extending into the vessel whereby the melt and the gas-liberatingmaterials are thoroughly mixed. The stirrer oi the stirring mechanism [8remains in the reaction vessel until it has traveled to station 20, atwhich time the stirrer is lifted out of the vessel and returned to theposition shown in Fig. 2 where it can be inserted into a freshly chargedreaction vessel to effect stirring of a new batch or charge. As thetable progresses clockwise, it reaches station 2| where the material inthe vessel is ejected by means of a piston-operated plunger 22. Whenmaterial is ejected from the vessel, it is deposited onto a rotatingtable 23 having a roller 24 adapted to roll over the material to coolthe same and also to reduce it to a desired thickness.

Feeder lfimaybe of anyconstructlon suitable for delivering measuredquantities of gas-liberating materials to the receptacles l2 to l5,inclusive,

as they are presented under trough 8 to receive phosphate melt. Asschematically illustrated, the feeder includes a storage hopper h, afeed cylinder f. c., a chute by which material is directed into therespective mixing chambers I 2l when a slide valve s. v. is opened torelease material from the cylinder. Slide valve s. v. may be operated byany suitable mechanism, for example, by means of a lever I pivoted at pand having one end connected to the valve s. v., a spring s being shownas urging the valve to closed position.

As shown more particularly in Fig. 3, each reaction vessel is providedwith a hinged bottom 25 which is held normally in closed position bymeans of a spring 26. The table 9 is provided with openings 21 of suchsize and shape that the hinged bottoms 25 may swing freely from closedto open position and vice versa. The vessels are provided with supportbrackets 30 by which they may be secured to the table.

Stirring mechanism 18 is carried on arm 32, the inner end of which issecured to a piston rod 33 having a piston 34 at its lower end disposedin a cylinder 35. The piston rod as shown is provided with a passageway36 extending through to the pressure face of piston 34 to allow theadmission of pressure fluid into the cylinder to raise the stirringmechanism out of a reaction vessel. The operation of the piston may becontrolled in any desired manner either automatically or manually. Forpresent purposes, it may be assumed that the control is manual by meansof a valve 38.

The ejecting piston 22 is carried by a piston rod 39 having a piston 40at its upper end working in a cylinder 4|. Pressure for operating thepiston to raise or lower it may be admitted to either end of thecylinder by means of a valve 42 which controls the supply of a pressurefluid to the cylinder.

Table 9 is arranged to be driven by means of a driving gear 43 meshingwith a ring gear 44 extending around the periphery of the table. The

.any suitable manner, being mounted on a rotating shaft or pedestal".

As the material passes under the cooling and thickness-adjusting roll24. the material may be scraped of! table 23 by means of a scraper 48which may be adjusted to any desired angular position.

The apparatus above described is, of course, only schematic and admitsof various modifications and changes suitable for carrying out theprocess of the invention and for making the product embodying theinvention.

A detailed description of the process and the product follows.

Phosphate glasses of various composition have been in use and arecurrently supplied to the trade for use as water softeners and for otherpurposes. These glassy phosphates as supplied to the trade are generallyin the form of irregular flat pieces resembling broken window glass,finely ground powder, round or semi-round beads, and thin flakes. Theflat pieces, the beads, and the powder have a relatively low surface toweight ratio, whereas the flakes have a high surface to weight ratio.

When added to water, both the irregular fiat window glass-like piecesand the beads dissolve very slowly as they sink to the bottom of thecontainer in which the solution is being made. Under such conditions, agelatinous coating forms on the surfaces of the phosphate particles asthere is not suflicient circulation developed to keep the surfaces cleanand free of the coating. To obtain relatively quick dissolution, thewindow glass-like pieces and the bead forms are usually suspended inwire mesh baskets or cloth bags at the surface of the water so that thesolution, which is heavier than the water, can set up a circulation thatkeeps the surfaces of the undissolved particles or pieces clean andreadily reactive with the water, whereby dissolution may proceed tocompletion at a relatively rapid rate, free of the hindering effect ofthe gelatinous coating above mentioned.

The powdered glass likewise settles to the bottom of the dissolvingwater accumulating in clumps and dissolving very slowly unless thesolution is agitated.

The thin flakes above mentioned when free of imperfectly formed flakes,dissolve very readily and rapidly when added directly to water, becauseeach flake has a very high surface to weight ratio. However, unlessconsiderable care is taken in the manufacture of the flakes, needle-likeparticles are formed which, if not screened or separated from theflakes, become a part of the finished product. These needle-likeparticles are relatively unobjectionable in commercial applications, butfor domestic or personal uses, they are objectionable in that they jagand prick the hands and skin, and produce a stinging, burning sensation.

My new article of manufacture is light and flufl'y, may be crushed inthe hands without danger of their being cut, and may be produced in theform of flat pieces of any desired size and thickness, or the pieces maybe crushed to a semi-powder form, 1. c., to a particle size that willpass a 30 mesh screen.

This product, because of its physical and chemical form, is free ofsharp cutting particles, has an extremely high rate of solution, and istherefore particularly suitable for home and personal uses as well asfor industrial purposes. The product, as stated above, has theproperties of the alkali-metal phosphate glasses, and the crystallinetripolyphosphate, one notable common property being that of softeningwater by the sequestering principle as disclosed by the U. S. HallPatent Re. 19,719. With respect to this myncw.producthasrcalcinmseqnestns on properties as. good: iffnpt' betterman-those funnszof sequestering: phosphate-preserrtiy arvaib able. Bythe term sequestering phosphates, I meansuchphosphates as will; softenwaterscons taming hardness-pmdncing'mineraasisuch asmh eium:and-magnesiumwithout precipitating such mineral or minerals, whether;or: not soap is added tolsuoh waters.

Although the, preparation of lightweight silioatezglassy'materials arecellular. or con.-

gas. bubbles is-not: new in, the art. phosphate material such a cellularstructure and possessing me'property of noleasinggases uponbeingdwolved' in: water toz-hasten; dissolution and'the methodof. makingtiresome are believedto be -new and .novel; .zima'ccordmice withtheinventimramequester ingphosphate may. be made.- whichzis light andhas: at glassy foam-like structure and contains entrapped gas bubbles,.andmay have undocumposed gas-liberatin material.

As a starting materialI may employ an alkali-metal phosphate glass suchassodium-phosabate glass, or mono-sodium dihydrogen: phosphoto, orphosphoric acid, and analkali-such as soda ash or potassium carbonate,sodium or pochloride inthe proportions which: will yield-a glass onquick quenching from the melt.

Ifra sodium phosphate glass is employed as-the averting material, thematerial is heated to its melting temperature orabove and held at thattemperature for a length of time which is sulfioient to insure-removalof water tq-a point where the melt preferably contains about 0.15%orxless by weight of" water. While the most. suitable product having afoam-like structure can be made by reducing the I water content to0.15%, .it is not absolutely essential to meet this requirement inpreparing an adequate-product of this structure. I he melt is' thencooled to a temperature near but above the melting point. If the body ofthe melt is large, the moltenphosphate ispouredor removed fromrthebodyof the melt. Into the portion of the'melt soremoved and while it isstill molten, a gas-liberai'ring 'ma- -terial is mixed. Duringthemixing, gas isliberated as the melt cools whereby a fiuffy foam-;like'-masscontainingcells of entrapped gas bubbles is formed. Afterthorough mixing of: the gas-liberating material. with the mass; the massis cooled as by quenching on. a relativeiy, cold metal surface. Wheresmalrbatches of the melt are being handled, the gas-liberating materialmay be stirred into the whole body of the-batch which is cooled rapidlyas above-described. to solidify the same. v i

I have found that by reducing the water con,- -tent.of-the melt to 0.15%orless-by weight before the gas-liberating material. is added, L obtaina. product which has an extremely uniform foam structure when cooled.Water is one of the vitrifying agents for phosphate glasses, but bydc.-creasing the water contentof the melt, I can pro.-

duce a glassy product havingaminutelycellular structure upon cooling;The water normally present in phosphate glasses has an effectzon therate at which the chemical reaction proceeds when-Iadd'an alkali-metalcarbonate to produce a=foam structure. If the water content is too:great, carbon dioxide may be liberated-from the carbonate too rapidly,and cause the formation -of:a;-non.-uniform product which may not-be soquickly: soluble; and: maycontariu-lcuttingrparticles. Also, byreducingithezwatmc'mntentrdf P glass melt below the percentage, normallypresent, the viscosity of the melt is increased; so that-unifonnentrapment of the car bon dioxide bubbles produced when I add-thealkali-metal carbonate is more readily accomplished. Although I.preferto reduce the water content of the melt to a predetermined low valuebefore adding a carbonate, I do not intend to limit my invention to amelt, the water content of 'whiclihas been so reduced, since I havefound it possible tomake a glass with a cellular structure from meltshaving a higher water content. Among the gas-liberating materialssuitable for my purpose are the carbonates such as soda ash, lithiumcarbonate, or potassium carbonate. Alkali-metal oxalates may also beused as a source of carbon dioxide for the purpose above described.

If a sodium phosphate glass is employed as a starting material, I mayuse a glass having a ratio of Nero to P205 within the range of about0.9: 1 to about 1.67:1. The more alkaline glasses. as well as the moreacid glasses, do not react as well with carbonate as do the glasseshaving ratios of Naz0:P2O5 between about 0.9:1 to the ratiocorrespondingto the peritectic which is about 1.4:1. I may also usemixed phosphate glasses such as sodium and potassium phosphate glass, ora mixture of potassium phosphate glass and sodium phosphate glass.

I' have made small batches of my new product employing as a startingmaterial, a sodium phospowdered ate added to the melt. The carbonate wasmixed with a glass stirring rod, stirring vigorously. With theliberation of CO2 the melt puffed up, and when it had puffed up to aboutmaximum volume, the mass was promptly removed from the crucible andplaced'on a cold metal plate, such as a steel plate. Another steel platewas then placed on the mass to quench it or quickly cool it. Theresulting product when solidified had a thickness of about s of an.inch. If the quenching plate is removed after only a few seconds, theresulting product is likely'to be'hard and almost entirely free fromcracks, but if the plate is permitted to remain in position for over 30seconds, the resulting mateml is friable and breaks readily into smallpieces.

I have found that similar results may be accomplished it'd-heat thephosphate glass toabout 750 C. and-hold itat this temperature for about1 hoursin the furnace before adding the carbomte' with concurrent"agitation and cooling as abovedescribed; A glass with a:cellularstructin'ebutless desirable can be produced simply by quickmelting.-

Althouglr 1:prefer-to add about 6% by-weight 'Of' carbonate-baseman theweight of the melt; I :may use from about 1% to about 12% by weightdependingion the a1kalinity=desired in the .ultimatez aqueous-solm ionz.My preferred-:product for household uses willzproduce a. pH in the range8=-9; imwarteirwzhen suficient material ISJJSed firtmsoflzenrthezwater;I continue agitation ot the mix after adding carbonate until it reachesits maximum volume, at which time I quickly remove the mass from thecrucible and cool it between steel plates as heretofore described. If Ido not use a quenching plate in cooling the product, the gas bubbles arenot as uniformly distributed.

In addition to preparing a water-soluble phosphate glass having a foamstructure from previously prepared phosphate glasses, I may also preparea glass having a similar structure starting with an orthophosphate, orother materials capable of producing a phosphate glass such as soda ashand phosphoric acid. I take 68 grams of mono-sodium orthophosphatemonohydrate a foam structure.

In addition to the batch processes which I have outlined above, I

phate glass, as a starting material, may be fed to a large furnace, thetemperature of which is held at about 1100 C., When the glass hasmelted, it may be retained in the furnace as a melt for about 15minutes. The melt is then from the mixer where reaction with the sodiumcarbonate has progressed to cause a foaming, the molten mass isdischarged onto a revolving steel appropriate scraping means.

Instead of charging the furnace with a prepared phosphate glass, I mayuse phosphoric acid and an alkali such as soda ash and heat the same andthere may be insuflicient gas permeation of the melt. I have found thatthe viscosity of the melt is satisfactory when the temperature thereofis within the range of about 600 C. to 750 C.

I prefer also that the melt should be dehydrated :to a low watercontent. If too much water is a bulk density of about trapped gasbubbles.

For the above reasons, it is apparent that the point where thegas-liberating material is added to the melt after issuing from thefurnace should be so located that the melt will have cooled to atemperature within the above indicated tempera- C. to 750 C.

when the gas-liberating materials is added as above described, a part ofit may become infused with the melt, but I believe that thegas-liberating material is only decomposed to an unknownexdecomposition. Thus, where soda ash is mixed into an (Z)Na2O(fIJ)P2O5melt (where .1: and 1 represent the mol proportions of NazO and P205, asmall portion of the soda. ash may remain unreacted in the melt while aportion may decompose to NazO and to CO2.

I have found that small pieces of foam phosphase glass produced by anyof the methods disclosed herein will completely disintegrate whendropped into 5 inches of water at a temperature of 40-45 C. with littleor no deposition of residual undissolved matter on the bottom of thevessel. The residual matter, if any, is soft and mushy and disappears ontouching with the fingers. Finely ground commercial phosphate glasses orflaked glass require a much longer period to dissolve and have inherentin them the the product produced by the preferred method.

The phosphate glass having a minutely cellular structure has a bulkdensity considerably lower than that of the commercial phosphate glassesMy product has a density in the range of from about 0.10.'7 gm./cc.,whereas the commercial glass in the form of thin flakes having athickness of the order of 0.001 to 0.005 inch has a density higher than1.2 gm./cc. Thus for example, a 4-8 mesh sample of my preferred producthas 0.3 gm./cc.

Having thus described my invention,'what I claim as new and desire tosecure by Letters Patent is:

1. As a new and useful product of manufacture a hardness sequesteringalkali-metal phosphate glass which is characterized by its rapid rate ofsolution in water, its multicellular foam-like structure, and its highdegree of friability, said phosphate glass being the product obtained byuntil it assumes a solid form.

2. The product as is 3. The method of making a rapidly water soluble,friable, hardness sequestering alkali-metal phosphate glass having amulticellular foam-like structure which comprises heating an alkalimetalphosphate capable of yielding a glass to a temperature in excess of themelting point of the mass and until the water content of the melt isbelow about 0.15 per cent by weight, mixing with the molten phosphate asolid alka imetal carbonate whereby carbon dioxide is liberated withinto form a foam-like mass, and cooling said mass to solidify the same.

4. The method of making a rapidly water soluble, friable,hardness-sequestering sodium phosphate glass having a multicellularfoam-like structure which comprises heating a sodium phosphate glass toa temperature in excess of the melting point of said glass, and untilthe water content of the melt is below about 0.15 per cent by weight,mixing with the molten phosphate a solid alkali-metal carbonate wherebycarbon dioxide is liberated within to form a foamlike mass, and coolingsaid mass to solidify the same.

5. The method as described in claim 4 characterized by the fact that thesodium phosphate glass used as the starting material has a molar ratioof NazOZPzOs of from about 0.9:1 to about 5:3.

6. The method as described in claim 4 characterized by the fact that theamount of a solid alkali-metal carbonate added is from about 1 per centto about 12 per cent by weight of the weight of the molten phosphate towhich it is added.

7. The method of making a rapidly water soluble, friable,hardness-sequestering alkali-metal phosphate glass having amulticellular foam-like structure which consists in heating analkalimetal phosphate capable of yielding a glass to a temperature inexcess of the melting point of said glass, forming a relatively largebody of molten alkali-metal phosphate, heating the molten phosphateuntil the water content thereof is less than 0.15 per cent based on theweight of the phosphate, causing the molten phosphate to flow from saidbody to a mixing station, adding a gas-liberating solid to said moltenphosphate at the mixing station, mixing said material into the melt atsaid station, and cooling the product until it assumes a solid form.

8. The method as described in claim 7 wherein the gas-liberating solidis an alkali-metal carbonate and the amount of gas-liberating solidadded is from about 1 per cent to about 12 per cent by weight based uponthe weight of the molten phosphate to which it is added.

ROBERT W. LIDDELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Hubbard et a1 Mar. 19, 1946

1. AS A NEW AND USEFUL PRODUCT OF MANUFACTURE A HARDNESS SEQUESTERINGALKALI-METAL PHOSPHATE GLASS WHICH IS CHARACTERIZED BY ITS RAPID RATE OFSOLUTION IN WATER, ITS MULTICELLULAR FOAM-LIKE STRUCTURE, AND ITS HIGHDEGREE OF FRIABILITY, SAID PHOSPHATE GLASS BEING THE PRODUCT OBTAINED BYHEATING AN ALKALI-METAL PHOSPHATE GLASS UNTIL MOLTEN, CONTINUING HEATINGUNTIL THE WATER CONTENT IS BELOW ABOUT 0.15% BY WEIGHT, ADDING THERETO ASOLID ALKALI-METAL CARBONATE WHEREUPON CARBON DIOXIDE IS LIBERATED ANDDISPERSED THROUGHOUT THE MELT, AND COOLING THE RESULTANT MIXTURE UNTILIT ASSUMES A SOLID FORM.